Biological valve for venous insufficiency

ABSTRACT

A bioprosthetic valve for repairing a deep venous insufficiency in a subject includes a single leaflet from a xenogeneic heart valve attached at natural margins of attachment to a patch of valve wall tissue. The patch may extend axially above and below the leaflet and circumferentially on either side of the leaflet to provide a region for attaching the patch to a fenestration in a host vein. A bioprosthetic valve may be manufactured by excising a portion of a xenogeneic heart valve including a single leaflet and contiguous wall tissue, and may further comprise shaving off excess leaflet tissue from adjacent leaflets. A method of replacing a malfunctioning venous valve in a subject includes providing a bioprosthetic valve as described above and inserting it to the host vein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/252,253, filed Oct. 15, 2008, which claims the benefit of U.S.Provisional Application No. 60/980,708, filed Oct. 17, 2007, the entiredisclosure of each of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

This application generally relates to a biological valve for thereplacement of a venous valve of the deep venous system of the leg orother veins of comparable caliber.

Description of the Related Art

Patients with chronic deep vein insufficiency may require the repair orreplacement of at least one of the venous valves of the deep veins ofthe leg. Also, in some cases the venous valve replacement may involvethe iliac veins.

Present therapy involves either the surgical repair of the valveleaflets or external banding of the vein to decrease the diameter andbring the weakened leaflets to a geometry which may allow for improvedfunction. The incompetent venous valves of patients with advancedchronic disease are usually not amenable to repair and may be replaced.

Currently, venous valve replacement and therapy is limited to allograftor cryopreserved valves. Allograft valves are difficult to harvest andcryopreserved valves can elicit a deleterious immune response.

SUMMARY OF EXEMPLARY EMBODIMENTS

In accordance with one embodiment, a monocusp bioprosthetic valve forimplantation into a host vein of a subject is described. Thebioprosthetic valve comprises biological tissue from a xenogeneicsource. The biological tissue comprises a single leaflet from a heartvalve and a patch comprising tissue contiguous with the single leaflet.In one aspect of the embodiment, the xenogeneic source is porcine. In afurther aspect, the single leaflet is attached to the patch at naturalmargins of attachment. In a still further aspect, the heart valve is anaortic valve. In such an aspect, the patch may include a segment of theaortic annulus. In the same aspect, the single leaflet may be anoncoronary leaflet. In yet another aspect of the embodiment, the patchhas a generally rectangular shape. In a further aspect, the patch has agenerally ovoid shape. In a still further aspect, the patch extendscircumferentially on either side of the leaflet so as to provide aregion for attachment to the host vein. In another aspect, the patchextends axially above and below the leaflet so as to provide a regionfor attachment to the host vein. In any of these aspects, at least aportion of the patch may be covered with a synthetic fabric. Also, inany of these aspects, the subject may be human.

In accordance with another embodiment, a bioprosthetic valve forimplantation into a host vein of a subject consisting essentially of asingle leaflet from a xenogeneic heart valve attached at natural marginsof attachment to a patch of valve wall tissue from the xenogeneic heartvalve is provided. In one aspect of this embodiment, the xenogeneicheart valve is porcine. In a further aspect, the patch extendscircumferentially on either side of the leaflet to provide a region forattachment to the host vein. In another aspect, the patch extendsaxially above and below the leaflet to provide a region for attachmentto the host vein. In yet another aspect, the xenogeneic heart valve isan aortic valve. In the preceding aspect, the leaflet may be anoncoronary leaflet.

In accordance with yet another embodiment, a method of manufacturing areplacement venous valve for a subject is described. The methodcomprises providing a xenogeneic heart valve which has at least oneleaflet and a valve wall, and which has been subjected to a fixationtreatment. The method further comprises excising a portion of the heartvalve. The portion comprises at least a selected leaflet attached atnatural margins of attachment to a patch of valve wall tissue, such thatsaid excised portion comprises a single leaflet. In one aspect of theembodiment, the xenogeneic heart valve is porcine. In another aspect,the patch extends circumferentially on either side of the selectedleaflet to provide a region for attachment to the host vein. In afurther aspect, the patch extends axially above and below the selectedleaflet to provide a region for attachment to the host vein. In a stillfurther aspect, the xenogeneic heart valve is an aortic valve. In suchan aspect, the selected leaflet may be a noncoronary leaflet. In yetanother aspect of the embodiment, the method further comprises cuttingthrough each of the natural commissures and shaving off tissue of anyleaflets adjacent to the selected leaflet. In any of these aspects, thesubject may be human.

In accordance with a further embodiment, a method of treating amalfunctioning valve in a host vein of a subject is described. Themethod comprises providing a replacement biological valve comprising asingle leaflet from a xenogeneic heart valve attached at natural marginsof attachment to a patch of contiguous tissue from the xenogeneic heartvalve. The method further comprises inserting said replacementbiological valve into said host vein. In one aspect of the embodiment,the method further comprises creating a fenestration in the host vein inthe region of the malfunctioning valve, the fenestration having a shapegenerally corresponding to the patch. In the preceding aspect, thefenestration may be created generally in the region of themalfunctioning valve, generally above the region of the malfunctioningvalve, or generally below the region of the malfunctioning valve. In thesame aspect, the method may further comprise attaching the replacementbiological valve to the host vein at the fenestration. In anotheraspect, the method further comprises removing at least one leaflet fromthe malfunctioning valve of the host vein. In a further aspect, thexenogeneic heart valve is a porcine aortic valve. In such an aspect, thesingle leaflet may be a noncoronary leaflet. In a still further aspect,the leaflet and patch have been subjected to a fixation treatment. Insuch an aspect, the fixation treatment may include exposing the leafletand patch to glutaraldehyde solution. In any of these aspects, thesubject may be human.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a front perspective view of a bioprosthetic valve accordingto an embodiment.

FIG. 1B is a front perspective view of a bioprosthetic valve accordingto an alternative embodiment.

FIG. 1C is a front perspective view of a bioprosthetic valve accordingto a further embodiment.

FIG. 1D is a front perspective view of a bioprosthetic valve accordingto another alternative embodiment.

FIG. 1E is a front perspective view of a bioprosthetic valve accordingto another alternative embodiment.

FIG. 1F is a front perspective view of a bioprosthetic valve accordingto a further embodiment.

FIG. 2 is an axial cross-sectional view of an aortic valve in closedposition, illustrating the trileaflet configuration of the aortic valve.

FIG. 3 is a front view of the aortic valve of FIG. 2 showing the valvecut along a commissure and laid open.

FIG. 4A is a longitudinal cross-sectional view of a vein with a normallyfunctioning venous valve shown in open position.

FIG. 4B is a longitudinal cross-sectional view of the vein of FIG. 4Awith the valve shown in closed position.

FIG. 5 is a longitudinal cross-sectional view of a vein with amalfunctioning venous valve. The vein is shown with a fenestration inwhich embodiments of the present invention may be implanted.

FIG. 6 is a longitudinal cross-sectional view of the host vein of FIG. 5with an embodiment of the present invention implanted therein.

FIG. 7 is a longitudinal cross-sectional view of another vein with amalfunctioning venous valve. The vein is shown with a fenestration inwhich alternative embodiments of the present invention may be implanted.

FIG. 8 is a longitudinal cross-sectional view of the host vein of FIG. 7with an alternative embodiment of the present invention implantedtherein.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE ASPECTS

The features, aspects and advantages of the present invention will nowbe described with reference to the drawings of various embodiments,which are intended to be within the scope of the invention hereindisclosed. These and other embodiments will become readily apparent tothose skilled in the art from the following detailed description of theembodiments having reference to the attached figures, the invention notbeing limited to any particular embodiment(s) disclosed.

Various embodiments provide a replacement venous valve comprising asingle biological valve leaflet configured to function under low-flow,low-pressure conditions of the deep venous system. Embodimentsadvantageously utilize the structural properties of biological valveleaflet tissue, preferably xenogeneic aortic valve leaflet tissue, toprovide a replacement venous valve offering hemodynamics matching thehemodynamics of the veins of the lower extremities.

Embodiments using tissue from an aortic valve in particular also takeadvantage of the unique shape of the aortic sinus to mimic the naturalflexibility and curvature of a normally functioning vein in the regionof a venous valve. These and other embodiments provide a desirablegeometry for opening and closing of a bioprosthetic valve in a hostvein, providing sufficient obstruction of the host vein in the closedposition and allowing for improved washing of the leaflet surface whenthe bioprosthetic valve is opened.

Certain embodiments incorporate a noncoronary leaflet of an aortic valvein a bioprosthetic valve, desirably providing a “clean” leafletcontaining significant amounts of collagen and elastin with minimalmuscle tissue attached thereto. Further, as the unique configuration ofthe aortic wall in the region of the noncoronary leaflet includes noexiting coronary arteries, these and other embodiments offer acontinuous surface for use as a patch in the wall of the host vein. ABioprosthetic Valve

With reference now to FIG. 1A, a bioprosthetic valve 100 according to anembodiment is illustrated. The bioprosthetic valve 100 generallyincludes a single leaflet 102 attached to a patch 104 at naturalcommissures 106(a), 106(b). The leaflet 102 has a free edge 103 whichresponds to differing pressures in the host vein to open and close thevalve 100.

As shown in the figure, the patch 104 may extend axially (with respectto the source vessel and the host vein) above and below the leaflet 102to provide upper and lower regions 108(a), 108(b) for attaching thebioprosthetic valve 100 to a host vein. Thus, in embodiments using anaortic valve source, the patch 104 may include a segment of the aorticannulus and/or a segment of the aortic wall.

The patch 104 may also extend circumferentially on either side of theleaflet 102, to provide lateral regions 110(a), 110(b) for attaching thebioprosthetic valve 100 to a host vein. The regions 110(a), 110(b) mayextend only minimally beyond the region of the leaflet 102, as shown inFIG. 1, or may extend further so as to partially or entirely encirclethe host vein upon implantation. The patch 104 may be generallyrectangular, as shown in FIG. 1, or may have any other suitable shape(such as circular, oval, or oblong) for implantation into a host vein.Although illustrated with the regions 108(a), 108(b) and 110(a), 110(b)extending substantially symmetrically above and below and on either sideof the leaflet 102, the patch 104 can of course extend about the leaflet102 by different lengths in different directions.

The bioprosthetic valve 100 and its component leaflet 102 may beselected and configured so that, with the valve 100 in a closedposition, the leaflet 102 provides adequate obstruction of the host veinat or near the site of the malfunctioning venous valve. The leaflet 102need not completely obstruct the host vein in the closed position,however, as some degree of backflow is acceptable in the venous system.Accordingly, with the valve 100 in a closed position, the free edge 103of the leaflet 102 may (but need not) contact an opposite wall of thehost vein continuously along the length of the free edge 103.

The bioprosthetic valve 100 may comprise tissue from any suitablexenogeneic source, such as a porcine, bovine, or equine heart valve. Theleaflet 102 may comprise a single leaflet from a heart valve, such as anoncoronary leaflet of an aortic valve. The patch 104 may comprise valvewall tissue which is contiguous with the leaflet. In certainembodiments, the patch 104 may include a segment of the aortic annulusand/or a segment of the aortic wall from the source valve. The patch 104may include part or all of that portion of the aortic wall which definesthe natural sinus for the leaflet 102. Including a portion of thenatural sinus advantageously provides a spatial buffer between theleaflet 102 and the valve wall when the valve 100 is in the openposition, both preventing or reducing adherence of the leaflet 102 tothe valve wall and facilitating closing of the valve 100 when flowpressure is reduced. Additionally, the patch 104 may be partially orentirely covered with a synthetic liner, such as a flexible syntheticfabric. Additionally or alternatively, the patch 104 may be sewn orotherwise attached to a larger backing or liner, or to a conduit or tubeconfigured for attachment to an external surface of the native vein.Such a backing or conduit can be used to coarct the vessel or otherwiseremodel the vessel wall. Such a backing or conduit may comprise aflexible biological and/or nonbiological material, depending on theneeds of the particular application.

With reference now to FIG. 1B, a bioprosthetic valve 150 according to analternative embodiment is illustrated. The valve 150 has a singleleaflet 152 attached to a patch 154 at natural margins of attachment156(a), 156(b). The leaflet 152 has a free edge 153 which responds todiffering pressures in the host vein to open and close the valve 150.

The patch 154 has a generally ovoid shape which extends axially (withrespect to the source vessel and the host vein) above and below theleaflet 152 to provide upper and lower regions 158(a), 158(b) forattaching the bioprosthetic valve 150 to a host vein. The patch 154 alsoextends circumferentially on either side of the leaflet 152, to providelateral regions 160(a), 160(b) for attaching the bioprosthetic valve 150to a host vein.

With reference now to FIG. 1C, a bioprosthetic valve 170 according to afurther embodiment is illustrated. The valve 170 has a single leaflet172 attached to a patch 174 at natural margins of attachment 176(a),176(b). The leaflet 172 has a free edge 173 which responds to differingpressures in the host vein to open and close the valve 170.

The patch 174 has a generally lenticular shape which extends axially(with respect to the source vessel and the host vein) above and belowthe leaflet 172 to provide upper and lower regions 178(a), 178(b) forattaching the bioprosthetic valve 170 to a host vein. The patch 174 alsoextends circumferentially on either side of the leaflet 172, to providelateral regions 180(a), 180(b) for attaching the bioprosthetic valve 170to a host vein. As shown in the figure, the upper and lower regions178(a), 178(b) may include pointed or angled sections allowing apractitioner to secure the valve 170 in an appropriate position and thenuse a continuous stitching pattern to close the anastomosis.

FIGS. 1D-1F illustrate additional embodiments. FIG. 1D shows abioprosthetic valve 182 having a single leaflet 186 attached to a patch184. As shown in the figure, the patch 184 has a shape that generallyfollows the contour of the interface between the leaflet 186 and thesource valve wall. Below the leaflet 186 and circumferentially on eitherside of the leaflet 186, the patch 184 extends beyond this contour toprovide an attachment region for the valve 182. Above the leaflet, thepatch 184 extends axially to approximately the same height as theleaflet 186 in an open position, so as to avoid interaction between theleaflet 186 and the natural wall of the host vessel. FIG. 1E shows abioprosthetic valve 188 having a single leaflet 192 attached to a patch190. The patch 190 has a similar shape to the patch 184 of FIG. 1D, butextends axially further above the leaflet 192. The patch 190 can thusinclude part or all of the tissue that defines the natural sinus for theleaflet 192. FIG. 1F shows a bioprosthetic valve 194 having a singleleaflet 198 attached to a substantially U-shaped patch 196. The patch196 includes the natural interface between the leaflet 198 and thesource valve wall and extends slightly beyond this interface to providean attachment region for the valve 194, without including the tissuethat defines the natural sinus for the leaflet 198.

In these and other embodiments, the inclusion of a contiguous wallportion that includes tissue taken from the donor vessel wall at anattachment region where the leaflet attaches to the vessel wall isconsidered advantageous at least because the attachment region includesa unique microstructure that is believed to enhance the ruggedness ofthe bioprosthetic valve. Retaining the natural margins of attachmentbetween the leaflet and vessel wall in the contiguous wall portion isconsidered particularly advantageous. For example, in an aortic valve,the margins of attachment (i.e., the leaflet anchorages) are composedprimarily of a dense collagenous tissue that provides a durableattachment between the leaflet and wall, which is expected to have abeneficial advantage on the longevity of a bioprosthetic valve thatincludes the margins of attachment.

Making a Bioprosthetic Valve

In some embodiments, after biological heart valve tissue to be used forthe replacement valve is first harvested, it may be stored in apreservative solution. The heart valve tissue may then be subjected to afixation or crosslinking treatment in order to preserve the materialfrom natural decay. Suitable fixation methods include exposing thetissue to a glutaraldehyde solution. Such a solution may comprise, forexample, 0.1%-1.0% glutaraldehyde in a buffer, such as a phosphate orcitrate buffer, formulated to maintain pH at between 6.0 and 8.0. Thetissue may be exposed to such a solution for a few minutes, up toseveral days, depending on the crosslinking reaction rate for a givensolution. The tissue may be fixed in a zero-stress environment.Alternatively, the tissue may be reinforced during fixation so as topreserve or enhance the curvature of the patch tissue or theconfiguration of the leaflet tissue. Tissue processed using the sameprocedures used by Hancock-Jaffe Laboratories of Irvine, Calif., tofabricate prosthetic heart valves may be used in the preparation ofbioprosthetic valves according to embodiments of the present invention.After crosslinking, the tissue can optionally be irradiated according toknown procedures with high energy X-radiation or gamma radiation, in anamount sufficient to sterilize the tissue without significantlydecreasing its tensile strength, so as to render the tissue moreflexible and compliant, and less antigenic. For example, in someembodiments, the irradiation procedures provided in U.S. Pat. No.4,798,611, the disclosure of which is incorporated herein by referencein its entirety, may be used. Next, a desired leaflet may be selectedfor use in a bioprosthetic valve, and a portion of the heart valveincluding at least the entire selected leaflet may be excised from thevalve.

FIG. 2 illustrates an aortic valve 200 which may be used in variousembodiments. As shown in FIG. 2, the aortic valve 200 has a trileafletconfiguration comprising a selected leaflet 202 and neighboring leaflets204 and 206. The selected leaflet 202 may, for example, be thenoncoronary leaflet of the aortic valve 200, which tends to be thecleanest of the leaflets (i.e., tends to have the least muscle) and alsohas the most predictable shape. The leaflets 202, 204, and 206 areattached to a valve wall 210 at natural commissures 212, 214, and 216.

Referring now to FIG. 3, the aortic valve 200 of FIG. 2 is shown cutalong the commissure 216 and laid open to better illustrate the threeleaflets 202, 204, and 206. According to various embodiments, the valvewall 210 and the leaflets 204, 206 may be cut, for example along lines220, 222, to separate the selected leaflet 202 and its contiguous valvewall tissue from the neighboring leaflets 204, 206. As can be seen bythe position of the lines 220, 222 in FIG. 3, the excised portion mayinclude a portion of the valve wall 210 extending circumferentially oneither side of the selected leaflet 202, so as to provide attachmentsurfaces comprising valve wall tissue on either side of the leaflet 202.The excised portion may include a portion of the aortic annulus 230and/or a portion of the aortic wall 232. Next, the commissures 212, 214of the selected leaflet 202 may be sliced through and the tissue of theadjacent leaflets 204, 206 may be removed, for example by shaving offthe adjacent leaflets, leaving the leaflet 202 attached to the aorticwall 232 at its natural margins of attachment. The valve wall tissuewhich is contiguous with the leaflet 202 may then be further trimmed inany desired shape and configuration suitable for attachment to a hostvein, such as, for example, the generally rectangular, generally ovoid,or generally lenticular shapes described above in connection with FIGS.1A-1C. The thickness of the contiguous wall portion can also be reducedso as to better match the thickness of the host wall, increasecompliance, and facilitate attachment of the wall portion to the hostvessel (for example by suturing or clipping). Suitable techniques forreducing tissue thickness include shaving, manual dissection,delamination, and other techniques.

Using a Bioprosthetic Valve

With reference now to FIGS. 4A-4B, a normally functioning venous valve400 is illustrated with valve leaflets 402(a), 402(b) shown in open(FIG. 4A) and closed (FIG. 4B) positions. FIG. 5, in contrast,illustrates a malfunctioning vein 500 with a non-functioning valveleaflet 502(a). A portion of the vein 500, including an opposing valveleaflet (not shown), has been excised to create a fenestration 504 inthe region of the incompetent valve leaflets. The fenestration 504 isshown extending through approximately half of the circumference of thevein 500, but may extend through more or less of the vein circumference.Further, although shown in the region of the incompetent native valve ofthe host vein 500, the fenestration 504 may be cut generally above orgenerally below the native valve. Additionally, depending on therequirements of the particular application, an entire segment of themalfunctioning vein 500 may be excised to prepare the vein forimplantation of various embodiments.

Referring now to FIG. 6, a bioprosthetic valve 600 according to anembodiment is shown implanted in the host vein 500. The bioprostheticvalve 600 includes a single leaflet 602 from a xenogeneic heart valveattached to a patch 604 of valve wall tissue from the xenogeneic source.The leaflet 602 has a free edge 603 which responds to differingpressures in the vein 500, to open and close the valve 600. As shown inthe figure, the weakened leaflet 502(a) may be removed from the vein 500prior to implantation of the bioprosthetic valve 600. Alternatively,depending on the condition of the weakened leaflet 502(a) and itslocation with respect to the fenestration 502, the weakened leaflet502(a) may be left in the host vein 500.

The bioprosthetic valve 600 is shown in FIG. 6 in a closed position,with the free edge 603 contacting the opposite wall of the host vein500. However, the free edge 603 need not contact the opposite wall ofthe host vein 500 continuously, or even at all, in order for the valveto function properly.

The patch 604 may generally match the size and shape of the fenestration502, and thus may be sutured or otherwise attached to the vein 500essentially flush with the fenestration 502, as shown in the figure.Alternative embodiments may comprise a patch which is slightly largerthan the fenestration, in which case the patch may be sutured orotherwise attached to the host vein in a generally overlappingconfiguration with the fenestration. Further, as mentioned above,embodiments may include a backing, liner, conduit, or tube secured tothe patch. In these and other embodiments, the patch may be indirectlysecured to the host vein via the backing, liner, conduit, or tube.

Referring now to FIGS. 7-8, another embodiment is illustrated. FIG. 7shows another malfunctioning vein 700 with a weakened valve leaflet702(a). A portion of the vein 700, including an opposing valve leaflet(not shown), has been excised to create a generally ovoid fenestration704 in the region of the incompetent valve leaflets. FIG. 8 illustratesthe vein 700 having a bioprosthetic valve 800 according to analternative embodiment implanted therein. The bioprosthetic valve 800includes a single leaflet 802 from a xenogeneic heart valve attached toa patch 804 of valve wall tissue from the xenogeneic source. The patch804 has a generally ovoid shape, corresponding to the ovoid shape of thefenestration 704. Providing a generally ovoid or oblong patch 804 mayadvantageously facilitate suturing and prevent leakagepost-implantation.

A method of replacing a malfunctioning venous valve is also provided.From a standard approach, a practitioner may excise a portion of thehost vein roughly corresponding in size and shape to a patch of abioprosthetic valve. Alternative embodiments may incorporate a backing,liner, conduit, or tube attached to the patch, in which case thepractitioner may excise a portion of the host vein roughly correspondingto the size and shape of the backing, liner, conduit, or tube. The patchof the bioprosthetic valve may comprise valve wall tissue which isnaturally contiguous with a single leaflet of a xenogeneic heart valve.The patch may be attached to the host vein (directly via the valve walltissue, or indirectly via the backing, liner, conduit, or tube) viasuturing or other suitable attachment means in the region of the excisedportion.

Depending on the particular circumstances, embodiments can be implantedeither above, below, or generally in the region of the incompetent valvebeing replaced. Any of these embodiments may involve removal of one ormore malfunctioning native leaflets prior to implantation of thebioprosthetic valve. Alternatively, depending on the circumstances, thenative leaflets may be left in the host vein.

Although standard-approach surgical methods have been described,embodiments of the invention may also be used with minimally invasivetechniques. For example, embodiments may be delivered and implantedendovascularly with the aid of an endovascular suturing device.Additionally, a practitioner could make a small inguinal incision andthen, with the aid of a scope and a biological glue, secure thebiological valve in place.

Embodiments can be used singularly or in multiples throughout the venoussystem, for example to repair deep vein insufficiencies below theinguinal ligament (i.e., for any vein in the leg) or in the common iliacvein. For example, in larger veins, two bioprosthetic valves accordingto embodiments may be implanted in opposing relationship to each otheron either side of a host vein to create a bileaflet valve geometry. Sucha configuration may be used in a region of the host vein away from aregion of incompetent valve. To achieve such a bileaflet geometry, twomonocusp valves can be implanted separately, with circumferential gapsbetween the valves. A composited bileaflet or trileaflet valve geometrycan also be achieved by attaching together two or three monocusp valvesas described above.

EXAMPLE Hemodynamic Evaluation of Valve Device

To evaluate the hydrodynamic performance and leaflet motioncharacteristics of a venous valve device according to the disclosure,several valve devices of various sizes were constructed and tested inthe aortic chamber of a pulsatile flow heart valve test apparatus.Hydrodynamic performance was observed under a range of conditionstypical of the upper leg of a human being. Leaflet function (i .e.,opening and closing) was confirmed for all valve devices under all testconditions studied.

Construction of Valve Devices

Three unconstrained diameters (10 mm, 12 mm, and 14 mm) believed to besuitable for valve devices intended to be implanted in a human vein wereselected for evaluation. For each unconstrained diameter, three valvedevices were constructed by attaching a gluteraldehyde crosslinkedbioprosthetic valve to a support frame by suturing. All specimens weresubmerged in saline following construction and subjected to irradiation.

Simulation of Compression for Loading into Percutaneous Delivery System

All specimens were loaded into a delivery catheter as shown in the TableI, and held in the compressed delivery configuration for at least 60(sixty) minutes prior to testing.

TABLE I Valve device unconstrained diameters and delivery sheath Frenchsize for simulation of loading compression Valve device unconstrainedDelivery sheath diameter (mm) French size (Fr) 10 14 12 16 14 18

Test System and Parameters

Each valve device was evaluated in the aortic chamber of a pulsatileflow apparatus from ViVitro Systems, Inc. (Victoria, British Columbia,Canada). Each valve device was sutured into a section of silicone tubingsized so as not to constrain the valve device. Arterial pressure wasadjusted to achieve the desired static pressure. Table II providesdetailed conditions under which the pulsatile flow analysis wasconducted for each valve device.

TABLE II Pulsatile flow test conditions Parameter Condition Testsolution Physiological saline maintained at 37 ± 1° C. Cycle rate 30 bbmCardiac output 1.2 L/min Static 15 mmHG ± 1, 35 mmHG ± 1, 50 mmHg ± 1,pressure 100 mmHG ± 1 Single stroke 70% with leaflet in open position,30% wave form with leaflet in closed position

Results

The valve devices were observed visually recorded on video taken fromthe outflow aspect of the valve device. At least ten measurements ofeach of the following variables were captured from ten consecutivecycles for each valve device under each static pressure condition: meanpressure difference across the valve device, mean and RMS flow ratesthrough the valve device, stroke volume, cycle rate, mean staticpressure over the entire cycle, duration of forward flow through thevalve device (as a percentage of cycle time), and regurgitant volume(including the closing, volume, leakage volume, and the correspondingmean pressure difference across the closed valve device).

Also, confirmation of opening and closing of the leaflet of each valvedevice was made through visual review of video recordings of thepulsatile flow test. Table III presents a summary of the visualconfirmations.

TABLE III Leaflet function based upon review of video recording ofpulsatile flow test Valve device Diameter Leaflet opening and closingconfirmed No. (mm) 15 mmHg 35 mmHg 50 mmHg 100 mmHg 1 10 yes yes yes yes2 10 yes yes yes yes 3 10 yes yes yes yes 4 12 yes yes yes yes 5 12 yesyes yes yes 6 12 yes yes yes yes 7 14 yes yes yes yes 8 14 yes yes yesyes 9 14 yes yes yes yes

CONCLUSION

Based on these results, it was concluded that the valve devices made inaccordance with the disclosure and tested as detailed above demonstratedacceptable leaflet function over the range of hemodynamic conditionsevaluated.

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. Therefore, it should be clearly understood thatthe forms of the invention described herein are illustrative only andare not intended to limit the scope of the invention.

What is claimed is:
 1. A method of providing a valve function in a hostvein of a subject, the method comprising: providing a biological valvecomprising a single leaflet xenogeneic heart valve tissue; attaching thesingle leaflet xenogeneic heart valve tissue at natural margins to apatch of contiguous tissue from the xenogeneic heart valve; insertingsaid replacement biological valve into said host vein at a patch site inthe host vein; and surrounding the host vein at the patch site with atube attached to the patch.
 2. The method of claim 1, further comprisingcreating a fenestration in the host vein, the fenestration having ashape generally corresponding to the patch.
 3. The method of claim 1,wherein the tube is created from a biological material.
 4. The method ofclaim 1, wherein the tube is created from a nonbiological material. 5.The method of claim 1, wherein the leaflet need not completely obstructthe host vein.
 6. The method of claim 2, further comprising attachingthe replacement biological valve to the host vein at the fenestration.7. The method of claim 1, further comprising removing at least oneleaflet from the malfunctioning valve of the host vein.
 8. The method ofclaim 1, wherein the xenogeneic heart valve is a porcine aortic valve.9. The method of claim 8, wherein the single leaflet is a noncoronaryleaflet.
 10. The method of claim 1, wherein the leaflet and patch havebeen subjected to a fixation treatment.
 11. The method of claim 10,wherein the fixation treatment includes exposing the leaflet and patchto glutaraldehyde solution.
 12. The method of claim 1, wherein thesubject is human.
 13. A method of manufacturing a replacement venousvalve for a host vein in a subject, the method comprising: obtaining axenogeneic heart valve, the heart valve having at least one leaflet anda valve wall, the heart valve having been subjected to a fixationtreatment; excising a portion of the heart valve, the portion comprisingat least a selected leaflet attached at natural margins of attachment toa patch of valve wall tissue, such that said excised portion comprises asingle leaflet; configuring the patch such that the patch is suitablefor attachment to said host vein; and attaching the patch to a tube, thetube configured to attach to an external surface of the host vein. 14.The method of claim 13, wherein the xenogeneic heart valve is porcine.15. The method of claim 13, wherein the patch extends circumferentiallyon either side of the selected leaflet to provide a region forattachment to the host vein.
 16. The method of claim 13, wherein thepatch extends axially above and below the selected leaflet to provide aregion for attachment to the host vein.
 17. The method of claim 13,wherein the xenogeneic heart valve is an aortic valve.
 18. The method ofclaim 17, wherein the selected leaflet is a noncoronary leaflet.
 19. Themethod of claim 13, further comprising cutting through each naturalcommissure of the selected leaflet and shaving off tissue of anyleaflets adjacent to the selected leaflet.
 20. The method of claim 13,wherein the subject is human.